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Date: Sat, 31 Mar 2018 00:24:37 -0700
From: Martin KaFai Lau <kafai@...com>
To: <netdev@...r.kernel.org>
CC: Alexei Starovoitov <ast@...com>,
Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>
Subject: [PATCH v2 bpf-next 03/10] bpf: btf: Check members of struct/union
This patch checks a few things of struct's members:
1) It has a valid size (e.g. a "const void" is invalid)
2) A member's size (+ its member's offset) does not exceed
the containing struct's size.
3) The member's offset satisfies the alignment requirement
The above can only be done after the needs_resolve member's type
is resolved. Hence, the above is done together in
btf_struct_resolve().
Each possible member's type (e.g. int, enum, modifier...) implements
the check_member() ops which will be called from btf_struct_resolve().
Signed-off-by: Martin KaFai Lau <kafai@...com>
Acked-by: Alexei Starovoitov <ast@...com>
---
kernel/bpf/btf.c | 206 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 206 insertions(+)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 4c421eb02848..7ac9486cf9b2 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -248,6 +248,10 @@ struct btf_kind_operations {
u32 meta_left);
int (*resolve)(struct btf_verifier_env *env,
const struct resolve_vertex *v);
+ int (*check_member)(struct btf_verifier_env *env,
+ const struct btf_type *struct_type,
+ const struct btf_member *member,
+ const struct btf_type *member_type);
void (*log_details)(struct btf_verifier_env *env,
const struct btf_type *t);
};
@@ -743,6 +747,16 @@ static int btf_df_check_meta(struct btf_verifier_env *env,
return -ENOTSUPP;
}
+static int btf_df_check_member(struct btf_verifier_env *env,
+ const struct btf_type *struct_type,
+ const struct btf_member *member,
+ const struct btf_type *member_type)
+{
+ btf_verifier_log_basic(env, struct_type,
+ "Unsupported check_member");
+ return -EINVAL;
+}
+
static int btf_df_resolve(struct btf_verifier_env *env,
const struct resolve_vertex *v)
{
@@ -759,9 +773,48 @@ static void btf_df_log(struct btf_verifier_env *env,
static struct btf_kind_operations df_ops = {
.check_meta = btf_df_check_meta,
.resolve = btf_df_resolve,
+ .check_member = btf_df_check_member,
.log_details = btf_df_log,
};
+static int btf_int_check_member(struct btf_verifier_env *env,
+ const struct btf_type *struct_type,
+ const struct btf_member *member,
+ const struct btf_type *member_type)
+{
+ u32 int_data = btf_type_int(member_type);
+ u32 struct_bits_off = member->offset;
+ u32 struct_size = struct_type->size;
+ u32 nr_copy_bits;
+ u32 bytes_offset;
+
+ if (U32_MAX - struct_bits_off < BTF_INT_OFFSET(int_data)) {
+ btf_verifier_log_member(env, struct_type, member,
+ "bits_offset exceeds U32_MAX");
+ return -EINVAL;
+ }
+
+ struct_bits_off += BTF_INT_OFFSET(int_data);
+ bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
+ nr_copy_bits = BTF_INT_BITS(int_data) +
+ BITS_PER_BYTE_MASKED(struct_bits_off);
+
+ if (nr_copy_bits > BITS_PER_U64) {
+ btf_verifier_log_member(env, struct_type, member,
+ "nr_copy_bits exceeds 64");
+ return -EINVAL;
+ }
+
+ if (struct_size < bytes_offset ||
+ struct_size - bytes_offset < BITS_ROUNDUP_BYTES(nr_copy_bits)) {
+ btf_verifier_log_member(env, struct_type, member,
+ "Member exceeds struct_size");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static s32 btf_int_check_meta(struct btf_verifier_env *env,
const struct btf_type *t,
u32 meta_left)
@@ -827,9 +880,61 @@ static void btf_int_log(struct btf_verifier_env *env,
const struct btf_kind_operations int_ops = {
.check_meta = btf_int_check_meta,
.resolve = btf_df_resolve,
+ .check_member = btf_int_check_member,
.log_details = btf_int_log,
};
+static int btf_modifier_check_member(struct btf_verifier_env *env,
+ const struct btf_type *struct_type,
+ const struct btf_member *member,
+ const struct btf_type *member_type)
+{
+ const struct btf_type *resolved_type;
+ u32 resolved_type_id = member->type;
+ struct btf_member resolved_member;
+ struct btf *btf = env->btf;
+
+ resolved_type = btf_type_id_size(btf, &resolved_type_id, NULL);
+ if (!resolved_type) {
+ btf_verifier_log_member(env, struct_type, member,
+ "Invalid member");
+ return -EINVAL;
+ }
+
+ resolved_member = *member;
+ resolved_member.type = resolved_type_id;
+
+ return btf_type_ops(resolved_type)->check_member(env, struct_type,
+ &resolved_member,
+ resolved_type);
+}
+
+static int btf_ptr_check_member(struct btf_verifier_env *env,
+ const struct btf_type *struct_type,
+ const struct btf_member *member,
+ const struct btf_type *member_type)
+{
+ u32 struct_size, struct_bits_off, bytes_offset;
+
+ struct_size = struct_type->size;
+ struct_bits_off = member->offset;
+ bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
+
+ if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
+ btf_verifier_log_member(env, struct_type, member,
+ "Member is not byte aligned");
+ return -EINVAL;
+ }
+
+ if (struct_size - bytes_offset < sizeof(void *)) {
+ btf_verifier_log_member(env, struct_type, member,
+ "Member exceeds struct_size");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static int btf_ref_type_check_meta(struct btf_verifier_env *env,
const struct btf_type *t,
u32 meta_left)
@@ -956,21 +1061,53 @@ static void btf_ref_type_log(struct btf_verifier_env *env,
static struct btf_kind_operations modifier_ops = {
.check_meta = btf_ref_type_check_meta,
.resolve = btf_modifier_resolve,
+ .check_member = btf_modifier_check_member,
.log_details = btf_ref_type_log,
};
static struct btf_kind_operations ptr_ops = {
.check_meta = btf_ref_type_check_meta,
.resolve = btf_ptr_resolve,
+ .check_member = btf_ptr_check_member,
.log_details = btf_ref_type_log,
};
static struct btf_kind_operations fwd_ops = {
.check_meta = btf_ref_type_check_meta,
.resolve = btf_df_resolve,
+ .check_member = btf_df_check_member,
.log_details = btf_ref_type_log,
};
+static int btf_array_check_member(struct btf_verifier_env *env,
+ const struct btf_type *struct_type,
+ const struct btf_member *member,
+ const struct btf_type *member_type)
+{
+ u32 struct_bits_off = member->offset;
+ u32 struct_size, bytes_offset;
+ u32 array_type_id, array_size;
+ struct btf *btf = env->btf;
+
+ if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
+ btf_verifier_log_member(env, struct_type, member,
+ "Member is not byte aligned");
+ return -EINVAL;
+ }
+
+ array_type_id = member->type;
+ btf_type_id_size(btf, &array_type_id, &array_size);
+ struct_size = struct_type->size;
+ bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
+ if (struct_size - bytes_offset < array_size) {
+ btf_verifier_log_member(env, struct_type, member,
+ "Member exceeds struct_size");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static s32 btf_array_check_meta(struct btf_verifier_env *env,
const struct btf_type *t,
u32 meta_left)
@@ -1073,9 +1210,35 @@ static void btf_array_log(struct btf_verifier_env *env,
static struct btf_kind_operations array_ops = {
.check_meta = btf_array_check_meta,
.resolve = btf_array_resolve,
+ .check_member = btf_array_check_member,
.log_details = btf_array_log,
};
+static int btf_struct_check_member(struct btf_verifier_env *env,
+ const struct btf_type *struct_type,
+ const struct btf_member *member,
+ const struct btf_type *member_type)
+{
+ u32 struct_bits_off = member->offset;
+ u32 struct_size, bytes_offset;
+
+ if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
+ btf_verifier_log_member(env, struct_type, member,
+ "Member is not byte aligned");
+ return -EINVAL;
+ }
+
+ struct_size = struct_type->size;
+ bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
+ if (struct_size - bytes_offset < member_type->size) {
+ btf_verifier_log_member(env, struct_type, member,
+ "Member exceeds struct_size");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static s32 btf_struct_check_meta(struct btf_verifier_env *env,
const struct btf_type *t,
u32 meta_left)
@@ -1136,6 +1299,7 @@ static int btf_struct_resolve(struct btf_verifier_env *env,
const struct resolve_vertex *v)
{
const struct btf_member *member;
+ int err;
u16 i;
/* Before continue resolving the next_member,
@@ -1143,6 +1307,7 @@ static int btf_struct_resolve(struct btf_verifier_env *env,
* type with size info.
*/
if (v->next_member) {
+ const struct btf_type *last_member_type;
const struct btf_member *last_member;
u16 last_member_type_id;
@@ -1151,6 +1316,14 @@ static int btf_struct_resolve(struct btf_verifier_env *env,
if (WARN_ON_ONCE(!env_type_is_resolved(env,
last_member_type_id)))
return -EINVAL;
+
+ last_member_type = btf_type_by_id(env->btf,
+ last_member_type_id);
+ err = btf_type_ops(last_member_type)->check_member(env, v->t,
+ last_member,
+ last_member_type);
+ if (err)
+ return err;
}
for_each_member_from(i, v->next_member, v->t, member) {
@@ -1169,6 +1342,12 @@ static int btf_struct_resolve(struct btf_verifier_env *env,
env_stack_set_next_member(env, i + 1);
return env_stack_push(env, member_type, member_type_id);
}
+
+ err = btf_type_ops(member_type)->check_member(env, v->t,
+ member,
+ member_type);
+ if (err)
+ return err;
}
env_stack_pop_resolved(env, 0, 0);
@@ -1185,9 +1364,35 @@ static void btf_struct_log(struct btf_verifier_env *env,
static struct btf_kind_operations struct_ops = {
.check_meta = btf_struct_check_meta,
.resolve = btf_struct_resolve,
+ .check_member = btf_struct_check_member,
.log_details = btf_struct_log,
};
+static int btf_enum_check_member(struct btf_verifier_env *env,
+ const struct btf_type *struct_type,
+ const struct btf_member *member,
+ const struct btf_type *member_type)
+{
+ u32 struct_bits_off = member->offset;
+ u32 struct_size, bytes_offset;
+
+ if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
+ btf_verifier_log_member(env, struct_type, member,
+ "Member is not byte aligned");
+ return -EINVAL;
+ }
+
+ struct_size = struct_type->size;
+ bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
+ if (struct_size - bytes_offset < sizeof(int)) {
+ btf_verifier_log_member(env, struct_type, member,
+ "Member exceeds struct_size");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static s32 btf_enum_check_meta(struct btf_verifier_env *env,
const struct btf_type *t,
u32 meta_left)
@@ -1239,6 +1444,7 @@ static void btf_enum_log(struct btf_verifier_env *env,
struct btf_kind_operations enum_ops = {
.check_meta = btf_enum_check_meta,
.resolve = btf_df_resolve,
+ .check_member = btf_enum_check_member,
.log_details = btf_enum_log,
};
--
2.9.5
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